Resonance damping for audio transducer systems

ABSTRACT

An apparatus ( 10 ) comprising: an audio transducer ( 201 ) configured to at least one of: generate sound upon receiving an audio signal provided by the apparatus ( 10 ); and convert sound into an audio signal to be processed by the apparatus ( 10 ); a housing component ( 301 ) comprising one or more sound apertures ( 303 ) configured to allow the transmission of sound through the one or more sound apertures ( 303 ); and an acoustic cavity ( 203 ) inside the apparatus ( 10 ) being acoustically coupled to the audio transducer ( 201 ) using the one or more sound apertures ( 303 ) wherein the one or more sound apertures ( 303 ) are configured to provide an acoustic damping.

RELATED APPLICATION

This application was originally filed as Patent Cooperation TreatyApplication No. PCT/CN2012/083129 filed Oct. 18, 2012.

FIELD

This invention generally relates to the fields of acoustics and audiotransducer integration and more specifically to the provision ofacoustic damping for resonances using micro apertures positioned betweenan audio transducer and an acoustic cavity.

BACKGROUND

Mobile devices often comprise audio components (e.g. speakers,microphones) integrated within the device. Such integration of the audiocomponents requires consideration of the mechanical and acousticproperties of the components that may at times conflict with the desiredacoustic characteristics. One of the considerations relates to acousticresonances when said transducers are integrated inside of a mobiledevice.

A speaker integration for hands free functionality should produce asufficient sound pressure level, an extended bandwidth (especially lowfrequency response), a low level distortion etc. However, such speakerintegration inside the device may start with disadvantages due tovarious reasons including magnet assembly being small, limited diaphragmarea, limited diaphragm excursion etc. In addition, the number of usecases is increasing in todays' devices but in contrast mechanicaldimensions are reduced therefore required air cavities associated withsaid speakers are forced to be reduced which influences the soundquality. The air cavities and acoustic apertures for speakerintegrations become vital because speaker elements including transducerdimensions, diaphragm, voice coil, suspension, and permanent magnetcannot be optimised to improve the sound quality.

There is a well-known physic concerning the rear cavity volume of thespeaker, which defines the sensitivity of the resulting speakerintegration and the low frequency limit of the resulting integration. Itis expressed as the larger the rear volume the lower the frequency oralternatively the larger the rear volume the higher the sensitivity.These rules came about because the volume inside the rear cavity has astiffness associated with it, which depends on the rear cavity volumeand the area of the speaker diaphragm that is compressing it. Therefore,the larger the diaphragm area the stiffer the air appears to be and thesmaller the rear cavity volume the stiffer the air appears to be. Inboth cases more force is required to compress the air inside the rearcavity volume. The fundamental resonance of a speaker integration, whichdoes not rely on any external electronic equalisation or feedback toextend the bass response, depends only on the mass of the driver, thecombined stiffness of the air inside the rear cavity volume and thesuspension of the diaphragm. The combination is stiffer than either thespeaker or the rear cavity volume on its own, and therefore theresonance frequency is higher. For such integrations to produce lowerfrequency components, a larger rear cavity volume is required which inturn exhibits a smaller stiffness and hence a lower system resonance.However, such larger rear cavity volume has an impact on the device sizetherefore a suitable trade off must be considered.

It is known that the resonance frequency position is important butfurthermore the shape of such resonance frequency is equally importantfor speaker integrations. Some speaker integrations can comprise a highquality factor (Q) which is a design parameter describing howunder-damped a resonance is and further characterizes a resonator'sbandwidth relative to its centre frequency. A high Q resonance is narrowband which rings at the resonance frequency. The rear cavity volume hasa low compliance when the speaker is acoustically coupled with the smallrear cavity volume. In these circumstances, such high Q resonances mayproduce an undesirable output signal at the resonance frequency unless adesired damping factor is applied which requires further designconsiderations. A typical frequency response of speaker integration maycomprise one or more resonances and at least one of these resonances maybe sharp peak comparing to the rest of the frequency response. It isunderstood that a suitable damping is introduced by means of anelectronic circuitry, one or more signal processing algorithms and/ormechanical components such as damping cloth, foam materials etc. It isknown that any of these considerations either individually or theircombinations define the shape of resonances.

SUMMARY

Aspects of this application thus provide a resonance damping for audiotransducers.

According to a first aspect there is provided an apparatus comprising:an audio transducer configured to at least one of: generate sound uponreceiving an audio signal provided by the apparatus; and convert soundinto an audio signal to be processed by the apparatus; a housingcomponent comprising one or more sound apertures configured to allow thetransmission of sound through the one or more sound apertures; and anacoustic cavity inside the apparatus being acoustically coupled to theaudio transducer using the one or more sound apertures wherein the oneor more sound apertures are configured to provide an acoustic damping.

The housing component may be at least one of: a PWB; a chassiscomponent; a rigid or semi-rigid structure; a sintered materialstructure; a cover; a cover structure; and a display window.

The housing component may be adjacent to the acoustic cavity forming acavity wall for the acoustic cavity.

At least one of the one or more sound apertures may have a diametersmaller than 0.5 mm.

The one or more sound apertures may be configured with characteristicsthat are selected to provide a predetermined acoustic characteristic.

The one or more sound apertures characteristics selected may include oneor more of: diameter; area; pitch; thickness; pitch/diameter ratio; andtotal open area.

The acoustic cavity may be formed as at least one of: a rear cavityvolume; and a front cavity volume, for the audio transducer.

The rear cavity volume may be substantially sealed inside the apparatusin such a way that air inside the rear cavity volume is prevented frommixing with the frontal sound waves produced by the audio transducer.

The sealed rear cavity volume may comprise sealing the acoustic couplingsurface of the audio transducer around the one or more sound apertures.

The acoustic cavity may comprise two parts bisected by the housingcomponent, such that a first part of the acoustic cavity is acousticallycoupled to the audio transducer using the one or more sound aperturesand a second part of the acoustic cavity is directly coupled to theaudio transducer.

The acoustic cavity may be substantially sealed.

The audio transducer may be at least one of: a speaker; and amicrophone.

According to a second aspect there may be provided a method comprising:providing an audio transducer configured to at least one of: generatesound upon receiving an audio signal provided by an apparatus; andconvert sound into an audio signal to be processed by the apparatus;providing a housing component comprising one or more sound aperturesconfigured to allow the transmission of sound through the one or moresound apertures; and providing an acoustic cavity inside the apparatusbeing acoustically coupled to the audio transducer using the one or moresound apertures wherein the one or more sound apertures are configuredto provide an acoustic damping.

The housing component may be at least one of: a PWB; a chassiscomponent; a rigid or semi-rigid structure; a sintered materialstructure; a cover; a cover structure; and a display window.

The method may further comprise locating the housing component adjacentto the acoustic cavity forming a cavity wall for the acoustic cavity.

At least one of the one or more sound apertures may have a diametersmaller than 0.5 mm.

The method may further comprise selecting at least one characteristic ofthe one or more sound apertures to provide a predetermined acousticcharacteristic.

The at least one characteristic may comprise one or more of: diameter;area; pitch; thickness; pitch/diameter ratio; and total open area.

Providing the acoustic cavity may comprise forming the acoustic cavityas at least one of: a rear cavity volume; and a front cavity volume, forthe audio transducer.

The method may further comprise sealing substantially the rear cavityvolume inside the apparatus in such a way that air inside the rearcavity volume is prevented from mixing with the frontal sound wavesproduced by the audio transducer.

Sealing substantially the rear cavity volume may comprise sealing theacoustic coupling surface of the audio transducer around the one or moresound apertures.

Providing the acoustic cavity may comprise forming the acoustic cavityin two parts bisected by the housing component, such that a first partof the acoustic cavity is acoustically coupled to the audio transducerusing the one or more sound apertures and a second part of the acousticcavity is directly coupled to the audio transducer.

Providing the acoustic cavity may comprise substantially sealing theacoustic cavity.

The audio transducer may be at least one of: a speaker; and amicrophone.

According to a third aspect there is provided an apparatus comprising:transducer means for at least one of: generating sound upon receiving anaudio signal provided by the apparatus; and converting sound into anaudio signal to be processed by the apparatus; housing means comprisingone or more sound apertures configured to allow the transmission ofsound through the one or more sound apertures; and cavity means insidethe apparatus being acoustically coupled to the transducer means usingthe one or more sound apertures wherein the one or more sound aperturesare configured to provide an acoustic damping.

The housing means may be at least one of: a PWB; a chassis component; arigid or semi-rigid structure; a sintered material structure; a cover; acover structure; and a display window.

The housing means may be adjacent to the cavity means forming a cavitywall for the cavity means.

At least one of the one or more sound apertures may have a diametersmaller than 0.5 mm.

The one or more sound apertures may be configured with characteristicsthat are selected to provide a predetermined acoustic characteristic.

The one or more sound apertures characteristics selected may include oneor more of: diameter; area; pitch; thickness; pitch/diameter ratio; andtotal open area.

The cavity means may be formed as at least one of: a rear cavity volume;and a front cavity volume, for the audio transducer.

The rear cavity volume may be substantially sealed inside the apparatusin such a way that air inside the rear cavity volume is prevented frommixing with the frontal sound waves produced by the transducer means.

The sealed rear cavity volume may comprise sealing the acoustic couplingsurface of the transducer means around the one or more sound apertures.

The cavity means may comprise two parts bisected by the housing means,such that a first part of the cavity means is acoustically coupled tothe transducer means using the one or more sound apertures and a secondpart of the cavity means is directly coupled to the transducer means.

The cavity means may be substantially sealed.

The transducer means may be at least one of: a speaker; and amicrophone.

Embodiments of the present application aim to address problemsassociated with the state of the art.

SUMMARY OF THE FIGURES

For better understanding of the present application, reference will nowbe made by way of example to the accompanying drawings in which:

FIG. 1 shows schematically an electronic device apparatus employing someembodiments;

FIG. 2 shows schematically the electronic device shown in FIG. 1 infurther detail;

FIG. 3 shows schematically an example sectioned view of a conventionalmobile apparatus speaker integration;

FIG. 4 shows schematically an example sectioned view of a mobileapparatus speaker integration according to some embodiments;

FIG. 5 shows schematically a further example sectioned view of a mobileapparatus speaker integration according to some embodiments;

FIG. 6 shows schematically an example three dimensional projection of amobile apparatus speaker integration according to some embodiments;

FIGS. 7a and 7b show schematically views of a printed wired board mobilespeaker integration according to some embodiments;

FIG. 8 shows schematically an example three dimensional view of platedand unplated through holes in the printed wiring board;

FIG. 9 shows a graph of an example mobile apparatus speaker integrationspeaker frequency response for conventional mobile speaker;

FIG. 10 shows a graph of an example frequency response for conventionalmobile speaker integration and mobile speaker integration according tosome embodiments;

FIG. 11 shows a graph of an example excursion for conventional mobilespeaker integration and mobile speaker integration according to someembodiments;

FIG. 12 shows a graph of an example mobile apparatus speaker integrationspeaker impedance response for conventional mobile speaker integrationand mobile speaker integration according to some embodiments;

FIG. 13 shows a graph of an example frequency response for conventionalmobile speaker integration and mobile speaker integration according tosome embodiments;

FIG. 14 shows schematically an example sectioned view of a mobileapparatus rear bass reflex speaker integration according to someembodiments; and

FIG. 15 shows schematically an example sectioned view of a mobileapparatus microphone integration according to some embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The following describes in further detail suitable apparatus andpossible mechanisms for an illustration of an example system comprisingthe known solution for a sound generating system. The apparatus as shownin FIG. 1 is in the form of a mobile phone. However it would beappreciated embodiments of the application may be implemented within anydevices or apparatus containing a transducer which may be a speakermodule. For example in other embodiments the apparatus can be anelectronic device such as a music player or a wireless communicationsystem, for example, a mobile telephone, a smartphone, a PDA, acomputer, a music player, a video player, or any other type of deviceadapted to output an audio signal.

The audio signal, such as a music signal, can as described herein besuitably processed using digital signal processing (DSP) together withan audio amplifier before the speaker module. The speaker module issuitably integrated inside the electronic device comprising one or moreacoustic cavities, one or more sound apertures to form a speaker system.

In an example embodiment, the audio signal such as a music signal, canbe processed in such a way that an equalizer, which can include a filterconfigured to reduce the vibration resonance of the speaker system whichmay comprise an high Q-factor resonance. It is known that a speakersystem with a sharp resonance may not produce a pleasant sound.

A multi-band dynamic range controller (DRC) in some embodiments couldprocess the audio signal in order to boost the energy of quieterfrequencies in a low frequency band. For example, a DRC band can beapplied for the lower frequency band aggressively whereas an alternativeDRC band can be applied to produce a softer effect for the upperfrequency band.

It is known that a speaker system for a portable device could bedesigned with either substantially sealed back cavity or an open backcavity or a back cavity with a bass reflex port. It is understood thatthe speaker integration resonance may possess different characteristicsbased on the integration type. For example where the speaker module isconfigured with a closed back cavity inside the apparatus, thefundamental resonance could occur in a range between 400 Hz to 1.2 kHz.A speaker system can be designed to have a very narrow fundamentalresonance (high Q-factor) at the resonance frequency which provides highenough sensitivity but produce a poor sound.

The speaker system as described herein comprises a moving coil speakermodule however similar integration methods and apparatus can be appliedto other types of transducer such as piezo and electrostaticloudspeakers. In such speaker integrations the back cavity requirementis also relevant and thus any speaker system radiating sound waves frontand back can benefit from the embodiments as described herein.

The mobile phone 10 may in some embodiments comprise an outer cover 100which houses some internal components. The outer cover 100 may comprisea display region 102 through which a display panel is visible to a user.The outer cover in some embodiments comprises a sound aperture 104. Inthese embodiments the sound aperture 104 may further include a separatebezel for the sound aperture 104 or in some other embodiments may beformed as part of the outer cover 100 or the display region 102. Whenthe sound aperture 104 is placed adjacent to a user's ear, soundgenerated by an earpiece module (not shown) is audible to the user. Themobile phone 10 may further comprise a volume control button 108 withwhich the user can control the volume of an output of the speakermodules. The mobile phone 10 comprises at least one sound outlet 114which may be used to radiate sound waves generated by a speaker module(not shown). The speaker module may be a loudspeaker and in someembodiments the loudspeaker can be a multi-function-device (MFD)comprising a vibra functionality wherein an electronic signal isconverted into a vibration. The MFD component having any of thefollowing: combined earpiece, integrated handsfree speaker, vibrationgeneration means or a combination thereof. In further embodiments themobile phone 10 comprises a separate vibra module in order to provide avibra functionality.

The speaker system may be used for handsfree operations such as musicplayback, ringtones, handsfree speech and/or video call. The soundoutlet 114 couples the acoustic output of the speaker module to exteriorof the mobile phone 10. In some embodiments, the sound outlet 114 maycomprise a suitable mesh structure or grill which may take variousforms, shapes or materials and which may be designed in relation to thefrequency response of the speaker module 114. The sound outlet 114 maybe structured as an array of individual small openings or may be asingle cross section area. The sound outlet 114 may be rectangular orcylindrical or may be any other suitable shape. At least one microphoneoutlet 112 for a microphone module (not shown) may be suitablypositioned in mobile phone 10 to capture the acoustic waves by at leastone microphone and output the acoustic waves as electrical signalsrepresenting audio or speech signals which then may be processed andtransmitted to other devices or stored for later playback.

The mobile phone 10 may provide interfaces enabling the user tointerface external devices or equipment to the mobile phone 10. Forexample an audio connector outlet 106 may be suitably positioned in themobile phone 10. In some embodiments, the audio connector outlet may besubstantially hidden behind a suitably arranged door or lid. The audioconnector outlet 106 may be suitable for connection with an audioconnector (not shown) or may be suitable for connection with an audio oraudio/visual (A/V) connector. The audio connector provides releasableconnection with audio or A/V plugs (not shown). These plugs provide anend-termination for cabling and are used to connect a peripheral deviceto the mobile phone 10. In this way, the mobile phone 10 is able tooutput audio or A/V and receive audio or A/V input. Such audio or A/Vplugs are often called round standard connectors and may be in differentformats which may comprise at least two contacts. The external devicesuch as a headset may itself comprise a microphone or suitableconnection for a microphone or further connection suitable for endterminating further cabling. The audio connector and/or associated plugmay be a standardized 2.5 mm or 3.5 mm audio connector and plug. It isaccordingly understood the audio connector outlet 106 may be formedcomprising a suitably arranged cross section area.

The mobile phone 10 may further comprise in some embodiments a universalserial bus (USB) interface outlet 110. The USB interface outlet 110 issuitably arranged for a USB connector (not shown). The mobile phone 10may further require a charging operation and therefore comprise acharging connector 116. The charging connector 116 may be of varioussizes, shapes and combinations or in some embodiments can be visually orsubstantially hidden.

In FIG. 2, a schematic block diagram of the exemplary mobile phone 10according to some embodiments is explained in further detail. The mobilephone 10 comprises a processing circuitry 20. The processing circuitry20 and the speaker module 30 are operationally coupled and any number orcombination of intervening elements can exist between them (including nointervening elements). The processing circuitry 20 is configured tooutput a suitable electrical signal to the speaker module 30 to generateacoustic signals. The electrical signal can in some embodiments be afirst component of an electrical audio signal, where the first componentcomprises a frequency band of the electrical audio signal comprising oneor more frequency components. The speaker module 30 is configured toconvert the first component into the acoustic signal. The processingcircuitry in some embodiments can output a second component of theelectrical audio signal to a different transducer, for example a vibramodule, providing the vibra function. The second component comprises alow-frequency band of the electrical audio signal. In alternativeembodiments the different transducer may be a second speaker module.

The electronic device 10 also comprises a memory 50, and a circuitry 40.

The processing circuitry 20 is configured to provide electrical outputsto the speaker module 30 and receives electrical inputs from thecircuitry 40. The processing circuitry may comprise adigital-to-analogue converter (DAC) to the speaker module. In someembodiments the speaker module may be used as an earpiece modulesuitable for handset speech call. The mobile phone 10 further comprisesat least one microphone and an analogue-to-digital converter (ADC)configured to convert the input analogue audio signals from the at leastone microphone into digital audio signals.

The mobile phone 10 may comprise multiple transducer modules that mayserve different use cases. An audio connector provides a physicalinterface to an external module such as a headphone or headset or anysuitable audio transducer equipment suitable to output from the DAC. Insome embodiments the external modules may connect to the mobile phone 10wirelessly via a transmitter or transceiver, for example by using a lowpower radio frequency connection such as Bluetooth A2DP profile. Theprocessor is further linked to a transceiver (TX/RX), to a userinterface (UI) and to a memory 22.

The processing circuitry and/or the circuitry may be configured toexecute various program codes. The implemented program codes may in someembodiments comprise individual settings for generating suitable audiosignals to the loudspeaker 33 and/or the second transducer. Theimplemented program codes may be stored for example in the memory forretrieval by the circuitry whenever needed. In some embodiments, thecodes are adaptively generated suitable for dedicated use cases. Thememory 50 could further provide a section for storing data, for exampledata that has been processed in accordance with the embodiments.

The speaker module 30 may comprise one or more magnets, a voice coil anda membrane. At least one of the magnets is an electromagnet. When anelectrical signal is provided to the electromagnet by the processingcircuitry 20, attraction and repulsion between the voice coil and atleast one magnet causes the membrane to move, which results in soundbeing produced by the speaker module 30.

As described herein mobile phone acoustic design is such that there canbe a problem regards to the excursion of a speaker being too large toimpact the reliability. In other words a sufficiently low resonancedamping can cause problems in the speaker transducer overshooting andphysically impacting the transducer membrane on a surface. Thus dampingcan prevent a speaker from damaging itself when being overdriven.Furthermore due to current design ethos there is a problem that thereare very few design variables which can be adjusted in a speaker systemintegration design and typically cavity volume (acoustic capacity) andopenings length and area (acoustic mass) are designed to change theresponse of the speaker.

For example a speaker typically used in a phone would have a Q-factor ashigh as 1.4 while a fourth order Butterworth vented design requires aQ-factor approximately 0.7 to 0.8. The concept behind embodiments asdescribed herein is to introduce a new and significantly more practicaland cheaper way to implement capillary damping for acoustic dampingpurposes. The acoustic damping can be used for example to prevent thespeaker from overshooting or applied in new structures as a tuneableelement for the speaker integration. An acoustic capillary typicallyrefers to a hole with a diameter which is very small typically less thanor equal to 0.2 mm. When the acoustic hole or capillary is small enoughthe resistance clue to the viscosity will be large enough to impact theresonance system of the speaker implementation. The concept behind thesecapillaries as described herein is to reuse the printed wiring board forprinted circuit board and in particular through holes within the printedwiring board as capillaries for acoustic damping purposes. Printedwiring board manufacture typically implements through holes as groundingbetween different layers. In the embodiments as described herein thediameter of the through holes can be made to a similar level as anacoustic capillary tube. Furthermore as described herein by adding orreusing copper plating within the inner side of a printed wiring boardhole as a heat conductive material the adiabatic compression of thesound wave in the hole produces a heating effect which produces aconstant temperature compression when copper capillaries are appliedadding further dampening effect because of the heat energy loss.

Implementation of the processing circuitry and/or the circuitry can bein hardware alone (a circuit, a processor . . . ), have certain aspectsin software including firmware alone or can be a combination of hardwareand software (including firmware).

The processing circuitry and/or the circuitry may be implemented usinginstructions that enable hardware functionality, for example, by usingexecutable computer program instructions in a general-purpose orspecial-purpose processor that may be stored on a computer readablestorage medium (disk, memory etc) to be executed by such a processor.

With respect to FIG. 3 a sectioned view of an example of a conventionalspeaker integration package within an apparatus is shown. The apparatusas shown in FIG. 3 comprises a chassis/cover 101 on which much of theapparatus is suspended, an outer cover 100 which surrounds the rear ofthe apparatus and is coupled to the rear of the chassis/cover 101, and adisplay assembly 102 at the front of the apparatus also coupled to thechassis/cover 101. Within the apparatus is located a printed wiringboard (PWB) 301 or printed circuit board (PCB) which is mounted on aninternal part of the chassis/cover 101 and on which one side of theprinted wiring board various electronic components can be mounted. Onthe underside of the printed wiring board 301 is located the speakermodule 201. Located adjacent to the speaker module and formed by a voidbetween the printed wiring board 301 and the chassis/cover 101 is therear or back cavity 203. As described herein the back cavity is a volumeof space which ‘tunes’ the speaker module 201. Within a conventionaldesign speaker integration design the back cavity 203 has a sealed backcavity of specific volume and shape to tune the speaker 201. However asdescribed herein ongoing design considerations require the reduction ofvolume of the back cavity 203 region and as such small back cavity 203volume of poor shape choice or design can lead to poor quality audioreproduction by the speaker 201 and/or possible damage of the speakermodule 201 due to a lack of control over the excursion.

With respect to FIG. 4 an example sectioned view of a mobile apparatusspeaker integration according to some embodiments is shown. Theapparatus comprises the cover 100 through which there is an opening104/114 through which the acoustic waves can pass. Beneath the cover 100and between the cover and the speaker module 201 is the front cavity205. Behind the front cavity 205 is the speaker module 201 (ortransducer). In the embodiments shown herein the speaker module 201 ismechanically fixed to the cover 100 to form a void between the cover 100and the speaker module 201 forming the front cavity 205. Formed in thevoid between the speaker 201 and the chassis and/or rear cover elementis the back cavity 203. The back cavity 203 in the example shown in FIG.4 is bisected or sectioned into at least two portions by the printedwiring board 301. In other words the acoustic cavity can be consideredto comprise at least two parts or portions of which at least two of theparts are separated by the printed wiring board 301. Within the printedwiring board 301 is located a plurality of capillaries 303 or tubes orholes which link the back cavity 203 sections. The one or morecapillaries (sound apertures) may be micro-holes provided by configuringthe structure where the micro-holes are positioned using parameters suchas diameter, pitch (distance between the centres of adjacentmicro-holes), area, thickness etc., and considerations of the type ofmaterial and surface finish of the structure. In some embodiments, thestructure and said micro-holes may be located and dimensioned in such away as to provide the best compromise between design, mechanics, andaudio requirements. Herein, the term capillary or micro-hole is used todescribe openings such as pores, holes, apertures, micro-apertures orthe like, which are substantially small for providing acoustic damping.Further, such openings may be circular or non-circular, for example,elliptic shape openings, slits, slots, regular or non-regular shapes, orthe like, may be provided in some embodiments.

In some embodiments the capillaries are through holes in the printedwiring board 301. Through holes in printed wiring boards are conduitswhich typically enable inter-layer electrical connections or couplingswhere the printed wiring board comprises multi-layers of electricallayouts. In other words the placement of suitable through holes in theprinted wiring boards can be used as the capillary couplings between theback cavity 203 sections.

Furthermore although in the following discussion the holes, capillaries,or tubes are described with respect to a component external to thespeaker (or microphone) housing, for example a printed wiring board ormesh, it would be understood that in some embodiments the partiallysealing member and the holes can be formed within the housing or moduleitself. For example in some embodiments the speaker (or microphone)module comprises a transducer and within the transducer housing is amaterial with the holes which dampens the response for a volume orcavity. In such embodiments one of the parts of the cavity exists atleast partially externally to the housing and one of the parts of thecavity exists completely internally to the housing with the housingmaterial operating as the sealing which is opened by the holes in thematerial. In some embodiments the material is the housing and the holesare in the housing allowing the flow of air between a first cavity partin the housing and a second cavity part external to the housing. In suchembodiments the manufacturer can thus place the single module inside theapparatus.

In some embodiments the transducer module (for example a speaker ormicrophone module) can comprise the acoustic cavity and the cavitydivider with the holes (capillaries or tubes) as well as the transducer.In such embodiments the transducer module is itself tuned in such a wayto dampen the Q-factor of the transducer without any external componentsrequired. In other words the transducer module can in such embodimentsbe inserted within the apparatus as a unit that requires only some smalladditional design or external design effort such as connecting orcoupling to the apparatus printed wiring board.

In some embodiments there can be more than one cavity divider. Forexample in some embodiments the transducer housing can comprise adivider material as described herein and the transducer housing belocated on a printed wiring board with further microholes, tubes orcapillaries, to define a first cavity part within the housing, a secondcavity part between the housing divider and to the printed wiring boardand a third cavity part between the printed wiring board and the casing(and in some embodiments, such as a front cavity, the acoustic hole(s)through which acoustic energy can pass through the casing). The size,spacing, distribution of the holes can be used to tune the resonance ofthe transducer.

With respect to FIG. 7a an example printed wiring board configurationswith through holes suitable for implementing capillary couplings betweenthe back cavity 203 sections is shown. The printed wiring board 301shown in FIG. 7a shows various through holes from large through holes601, medium through holes 603 and small through holes 605. It would beunderstood that the location, size and arrangement of the through holesis at least partially dependent on the printed wiring board electricalcircuit layout, however it would be understood that in some embodimentsthe area of the printed wiring board used for the through holes in someembodiments can be an electrically isolated section from the rest of theelectrical circuitry. Furthermore it would be understood thatconventional printed wiring board manufacturing such as printed wiringboard PTH (Plated Through Hole) technology can drill mechanicalcapillaries as small as 0.2 mm without the need for additional tooling.

In some embodiments rather than re-use through holes which have beendesigned with respect to the printed wiring board to couple electricalcircuitry additional through holes can be added. These can either bedrilled, for example using PTH technology or using additional tooling toreduce the diameter or spacing of the holes. With respect to FIG. 7b anexample printed wiring board configuration with an array 791 ofadditional through holes 611 are. In the example shown in FIG. 7b the25×16 capillary grid is generated using laser burning to achieve a holediameter less than 0.2 mm. Although the grid 791 of the through holes611 are shown in a rectangular grid or array it would be understood anysuitable two-dimensional configuration, layout or spacing of the throughholes can be implemented.

In general the acoustic resistance of a capillary system can beexpressed as the following formula:

$R = {\rho\; c{\frac{0.147}{d^{2}} \cdot \frac{t}{p} \cdot \left( {\sqrt{1 + \frac{x^{2}}{32}} + {\frac{\sqrt{2}x}{8} \cdot \frac{d}{t}}} \right)}}$

Where:

${x = {\sqrt{\frac{\rho\omega}{\eta}} \cdot \frac{d}{2}}};$d is the diameter of capillary; η is the viscosity coefficient; t is thelength of the capillary; p is the ratio of opening area and total area;ρ is the density of air; and c is the sound velocity in the air.

From the above formula, it can be easily found that the diameter, lengthand opening percentage of an area can decide the total resistance.However it would be understood that the length of the capillary, whichin the above embodiments equals the thickness of PWB, is usually fixed.

The array grid as shown in FIG. 7b when implemented in a speaker moduleimplementation such as shown in FIG. 3 was tested and the resultantfrequency response and speaker impedance response (Q-factor) shown inFIGS. 13 and 12 respectively.

For example in FIG. 12 the speaker impedance response for both a PWBnon-capillary sealed back cavity speaker implementation shown by trace1103 and the sealed back cavity with PWB capillaries speakerimplementation (as described herein) shown by trace 1101 is shown. Thecapillaries significantly reduce the Q-factor and furthermore theexcursion is reduced from 0.63 mm to 0.41 mm a 35% reduction.

FIG. 13 shows the speaker frequency response for both a PWBnon-capillary sealed back cavity speaker implementation shown by trace1201 and the sealed back cavity with PWB capillaries speakerimplementation (as described herein) shown by trace 1203 is shownshowing that these speaker frequency responses are substantiallysimilar.

With respect to FIG. 6 an example three-dimensional projection of amobile apparatus speaker integration is shown where the speaker module201 is coupled electrically via a leaf spring 503 to the printed wiringboard 301 in the form of a printed wiring board pad or PPP. The PPP(Pick-Place-Plate) can be used to reduce the contact resistance of anacoustic contact pin and PWB. The leaf spring 503 or any other suitableresilient member in some embodiments can mechanically bias the speakermodule 201 from the printed wiring board 301 sufficiently to create afirst void forming part of the back cavity 203.

In some embodiments the speaker module can be designed such that thecasing of the speaker module is mechanically coupled to the printedwiring board. Although the following example show a rear cavity sectionbetween the speaker module 201 and the printed wiring board, it would beunderstood that in some embodiments the volume of rear cavity sectionbetween the speaker module 201 and the printed wiring board 301 iscompletely within the speaker module 201. In other words the speakermodule is located on the printed wiring board 301 and the speaker modulehas an open face located over the capillary arrangement.

With respect to FIG. 5 further example of the implementation ofcapillary damping is shown wherein the back cavity 203 is separated intotwo sections by a printed wiring board or similar sectioning part 400 onwhich is mounted a damping mesh 401. The damping mesh 401 can forexample be a material layer with suitable capillary or hole array todamp the transfer of air between the back cavity sections. It would beunderstood that the damping mesh 401 can be fixed within or under thesectioning part 400, or in some embodiments may be a multi-layer meshstructure.

For example with respect to FIG. 9 an example frequency response for amesh structure such as shown in FIG. 5 is shown. The graph in FIG. 9shows frequency response for an acoustic damping Sefar 160-20 mesh with4 layers. The mesh opening area has a diameter of 4 mm in a 13 mm×18 mmsquare section. As can be seen in FIG. 9 the difference betweenfrequency responses between a capillaries—mesh structure trace or plot803 and the empty or no mesh structure as shown by trace or plot 801 isminor. However the same examples show an excursion reduction from 0.633mm to 0.457 mm.

Furthermore simulations show similar improvements. For example anexample simulated high sensitivity speaker, which is 13×18×4.5 mm insize with sensitivity 87dBSPL/1V/0.1 m; and with 700 mW power handlingcapacity implementation where there are 400 capillaries made in an 18mm×13 mm square, and each capillary has the diameter 0.15 mm where andthe printed wiring board is 0.8 mm high can be simulated which producesa frequency response such as shown in FIG. 10 where the trace of thefrequency response without the capillaries 901 is similar to the traceof the frequency response of the simulated example capillaryimplementation 903. The simulated examples produce a sensitivity drop ofonly 1 dB.

Furthermore with respect to FIG. 11 the simulated excursion with andwithout the capillary implementations is shown. The excursion withoutcapillary implementation shown by trace 1001 and with capillaryimplementation shown by trace 1003 difference shows that the excursiondrops by 20%.

As an improvement to normal capillary material, in some embodiments theuse of PWB capillary or holes can be further improved by the layer orplating of copper in the inner side of capillary which is good heatingconductive material compared with normal material. With respect to FIG.8 a plated and un-plated through hole configuration is shown. On theleft-hand side of FIG. 8 an un-plated through hole 701 is shown throughthe printed wiring board 301. The right-hand side of FIG. 8 shows theprinted wiring board 301 with a through hole 701 which is plated 703. Itwould be understood that the plating or a conductive material, forexample copper, would enable a temperature or heat absorption element tobe added to the damping characteristics where the heating exchange ofbetween the air and copper absorbs more energy when sound is spreadingthrough the capillary. In other words the resistance is increased in thecapillary leading to additional damping effect. In theory the resistancecan be increased to:

$R = {\rho\; c{\frac{0.335}{d^{2}} \cdot \frac{t}{p} \cdot \left( {\sqrt{1 + \frac{x^{2}}{32}} + {\frac{\sqrt{2}}{8} \cdot \frac{xd}{t}}} \right)}}$

The capillaries perform acoustic damping which can be configured toprevent the speaker from overshooting or applied as a tunable elementwithin the back cavity 203.

With respect to FIG. 14 a further configuration of the hole or capillarydamping is shown with respect to a vented box (or bass reflex)configuration. The configuration as shown in FIG. 14 is similar to thatshown in FIG. 4 is shown where the back cavity 203 is vented by a vent1301. However the mesh or printed wiring board separator 401 is shownbetween the speaker and the two rear cavities 203.

In the examples shown above the micro-hole or capillary damping is shownwith respect to the rear acoustic cavity damping and furthermore withrespect to a speaker transducer. However it would be understood that theapplication of micro-hole or capillary damping can be applied to frontacoustic cavity damping. Furthermore it would be understood that in someembodiments the micro-hole or capillary damping can be applied to amicrophone transducer implementation.

With respect to FIG. 15 an example sectioned view of a mobile apparatusmicrophone integration where micro-hole or capillary damping is appliedto the front chamber is shown. The mobile apparatus comprises the cover100 through which there is an opening 114 through which the acousticwaves can pass. Beneath the cover 100 and between the cover and themicrophone module 1401 is the front cavity 205. Behind the front cavity205 is the microphone module 1401 (or transducer). In the embodimentsshown herein the microphone module 1401 is mechanically fixed to theprinted wiring board 301 and sealing rubber sections 1405, 1407, and1409 form a void between the cover 100 and the microphone module 1401forming the front cavity 205. The front cavity 205 in the example shownin FIG. 15 is bisected or sectioned into at least two portions by theprinted wiring board 301. Within the printed wiring board 301 is locateda plurality of capillaries 1403 or tubes or holes which link the frontcavity sections. In the example shown herein the front cavity 205 isbisected into a first part 205 ₂ which is directly coupled to themicrophone module 1401 and a second part 205 ₁ which is coupled to themicrophone module 1401 via the capillaries 1403 (and via the frontcavity first part 205 ₂).

In the example shown in FIG. 15 the capillaries are formed orimplemented within the printed wiring board, however it would beunderstood that in some embodiments the frequency dependent dampening(to reduce the Q-factor peak) can be implemented by locating thecapillaries within the cover 100 or other part of the cavity perimeter.In other words the front cavity is damped by the implementation ofcapillaries which selectively frequency dampen the air flow in to andout of the cavity rather than through the cavity.

In the embodiments described herein the term cavity or acoustic cavitycan be understood to be any acoustically configured volume, typically ofair, but can be of any gaseous, liquid or otherwise material suitablefor conducting and by virtue of the cavity walls filter acoustic wavesinto or from the transducer. As such the cavity can be an acoustic spacesuch as an acoustic channel, an acoustic conduit or acoustic chamber.

It shall be appreciated that the term user equipment is intended tocover any suitable type of wireless user equipment, such as mobiletelephones, portable data processing devices or portable web browsers,as well as wearable devices.

Furthermore elements of a public land mobile network (PLMN) may alsocomprise apparatus as described above.

In general, the various embodiments of the invention may be implementedin hardware or special purpose circuits, software, logic or anycombination thereof. For example, some aspects may be implemented inhardware, while other aspects may be implemented in firmware or softwarewhich may be executed by a controller, microprocessor or other computingdevice, although the invention is not limited thereto. While variousaspects of the invention may be illustrated and described as blockdiagrams, flow charts, or using some other pictorial representation, itis well understood that these blocks, apparatus, systems, techniques ormethods described herein may be implemented in, as non-limitingexamples, hardware, software, firmware, special purpose circuits orlogic, general purpose hardware or controller or other computingdevices, or some combination thereof.

The embodiments of this invention may be implemented by computersoftware executable by a data processor of the mobile device, such as inthe processor entity, or by hardware, or by a combination of softwareand hardware. Further in this regard it should be noted that any blocksof the logic flow as in the Figures may represent program steps, orinterconnected logic circuits, blocks and functions, or a combination ofprogram steps and logic circuits, blocks and functions. The software maybe stored on such physical media as memory chips, or memory blocksimplemented within the processor, magnetic media such as hard disk orfloppy disks, and optical media such as for example DVD and the datavariants thereof, CD.

The memory may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor-based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory. The data processors may be of any type suitable tothe local technical environment, and may include one or more of generalpurpose computers, special purpose computers, microprocessors, digitalsignal processors (DSPs), application specific integrated circuits(ASIC), gate level circuits and processors based on multi-core processorarchitecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various componentssuch as integrated circuit modules. The design of integrated circuits isby and large a highly automated process. Complex and powerful softwaretools are available for converting a logic level design into asemiconductor circuit design ready to be etched and formed on asemiconductor substrate.

Programs, such as those provided by Synopsys, Inc. of Mountain View,Calif. and Cadence Design, of San Jose, Calif. automatically routeconductors and locate components on a semiconductor chip using wellestablished rules of design as well as libraries of pre-stored designmodules. Once the design for a semiconductor circuit has been completed,the resultant design, in a standardized electronic format (e.g., Opus,GDSII, or the like) may be transmitted to a semiconductor fabricationfacility or “fab” for fabrication.

The foregoing description has provided by way of exemplary andnon-limiting examples a full and informative description of theexemplary embodiment of this invention. However, various modificationsand adaptations may become apparent to those skilled in the relevantarts in view of the foregoing description, when read in conjunction withthe accompanying drawings and the appended claims. However, all such andsimilar modifications of the teachings of this invention will still fallwithin the scope of this invention as defined in the appended claims.

What is claimed is:
 1. An apparatus comprising: a speaker system whereinthe speaker system comprises: an audio transducer configured to generatesound; a housing component of the apparatus comprising one or more soundoutlets configured to allow the transmission of sound in a firstdirection out of the apparatus, a second housing component comprisingone or more sound apertures comprising capillaries configured to allowthe transmission of sound from the audio transducer in a seconddirection different from the first direction and through the one or moresound apertures, wherein the audio transducer is located between the oneor more sound outlets and the one or more sound apertures; and anacoustic cavity of the speaker system inside the apparatus beingacoustically coupled to the audio transducer using the one or more soundapertures wherein the one or more sound apertures are configured toprovide an acoustic damping; wherein the apparatus comprises at leastone processor configured to execute operations of the apparatus.
 2. Theapparatus as claimed in claim 1, wherein the second housing component isone of: a printed wiring board; a chassis component; a rigid orsemi-rigid structure; a sintered material structure; and adjacent to theacoustic cavity forming a cavity wall for the acoustic cavity andwherein the housing component is one of: a cover; a cover structure; adisplay window.
 3. The apparatus as claimed in claim 1, wherein at leastone of the one or more sound apertures have a diameter smaller than 0.5mm.
 4. The apparatus as claimed in claim 1, wherein the one or moresound apertures comprising capillaries are configured to providecharacteristics that are selected to provide a predetermined acousticcharacteristic.
 5. The apparatus as claimed in claim 4, wherein the oneor more sound apertures characteristics selected include one or more of:diameter; area; pitch; thickness; pitch/diameter ratio; and total openarea.
 6. The apparatus as claimed in claim 1, wherein the acousticcavity is formed as at least one of: a front cavity volume extendingfrom the audio transducer in the first direction; and a rear cavityvolume extending from the audio transducer in the second directiondifferent from the first direction, for the audio transducer.
 7. Theapparatus as claimed in claim 6, wherein the rear cavity volume issubstantially sealed inside the apparatus in such a way that air insidethe rear cavity volume is prevented from mixing with the frontal soundwaves produced by the audio transducer.
 8. The apparatus as claimed inclaim 7, wherein the sealed rear cavity volume comprises sealing theacoustic coupling surface of the audio transducer around the one or moresound apertures.
 9. The apparatus as claimed in claim 1, wherein theacoustic cavity comprises two parts bisected by a wall of the secondhousing component, such that a first part of the acoustic cavity isacoustically coupled to the audio transducer using the one or more soundapertures and a second part of the acoustic cavity is directly coupledto the audio transducer.
 10. A method comprising: providing a speakersystem within an apparatus wherein the speaker system comprises an audiotransducer; providing a housing component of the apparatus comprisingone or more sound outlets configured to allow the transmission of soundin the first direction out of the apparatus, and providing a secondhousing component comprising one or more sound apertures configured toallow the transmission of sound from the audio transducer in a seconddirection different from the first direction and through the one or moresound apertures, the one or more sound apertures comprising capillarieswherein the audio transducer is located between the one or more soundoutlets and the one or more sound apertures; and providing an acousticcavity of the speaker system inside the apparatus being acousticallycoupled to the audio transducer using the one or more sound apertureswherein the one or more sound apertures are configured to provide anacoustic damping; wherein the apparatus comprises at least one processorconfigured to execute operations of the apparatus.
 11. The method asclaimed in claim 10, wherein the second housing component is at leastone of: a PWB; a chassis component; a rigid or semi-rigid structure; anda sintered material structure; and wherein the housing component is oneof a cover; a cover structure; and a display window.
 12. The method asclaimed in claim 10, further comprising locating the second housingcomponent adjacent to the acoustic cavity forming a wall for theacoustic cavity.
 13. The method as claimed in claim 10, wherein at leastone of the one or more sound apertures have a diameter smaller than 0.5mm.
 14. The method as claimed in claim 10, further comprising selectingat least one characteristic of the one or more sound aperturescomprising capillaries to provide a predetermined acousticcharacteristic.
 15. The method as claimed in claim 14, wherein the atleast one characteristic comprises one or more of: diameter; area;pitch; thickness; pitch/diameter ratio; and total open area.
 16. Themethod as claimed in claim 10, wherein providing the acoustic cavitycomprises forming the acoustic cavity as at least one of: a front cavityvolume extending from the audio transducer in the first direction; and arear cavity volume extending from the audio transducer in the seconddirection different from the first direction for the audio transducer.17. The method as claimed in claim 16, further comprising sealingsubstantially the rear cavity volume inside the apparatus in such a waythat air inside the rear cavity volume is prevented from mixing with thefrontal sound waves produced by the audio transducer.
 18. The method asclaimed in claim 17, wherein sealing substantially the rear cavityvolume comprises sealing the acoustic coupling surface of the audiotransducer around the one or more sound apertures.
 19. The method asclaimed in claim 10, wherein providing the acoustic cavity comprisesforming the acoustic cavity in two parts bisected by a wall of thesecond housing component, such that a first part of the acoustic cavityis acoustically coupled to the audio transducer using the one or moresound apertures and a second part of the acoustic cavity is directlycoupled to the audio transducer.
 20. The apparatus as claimed in claim1, wherein inner surfaces of the capillaries are plated with aconductive material.
 21. The apparatus as claimed in claim 20, whereinthe conductive material is copper.
 22. The apparatus as claimed in claim1, wherein the transmission of sound from the audio transducer in thesecond direction different from the first direction is further ventedout of the apparatus by a vent.
 23. The method as claimed in claim 10,wherein inner surfaces of the capillaries are plated with a conductivematerial.
 24. The method as claimed in claim 10, further comprisingventing the transmission of sound from the audio transducer based on thesecond direction out of the apparatus.